Longitudinal analysis of mortality from breast cancer in Japan, 1950–1993: fitting Gompertz and Weibull functions

Abstract

Age-specific mortality rates from breast cancer (BC) in Japan from 1950 through 1993 were subjected to longitudinal Gompertzian and Weibull analyses. Age-specific BC mortality rate distributions between the ages of 30 and 75 years were Gompertzian in each year. Between 1950 and 1993, age-adjusted BC mortality rates increased by 65%. Gompertzian analysis might suggest that increasing mortality rates for BC can be attributed to worsening environmental influences during that period, especially after 1970. This suggests that the environmental factor has changed to account for increasing mortality from BC. The environmental factor increased 16% during that period and the competitive environmental factor was two times more contributory to mortality from BC in 1993 as compared with 1950. Age-specific mortality rates from BC were better fitted to the Weibull than the Gompertz function. The parameters of a and τ in the Weibull function ranged between 2.9 and 3.5 and between 8.5 and 13.0 respectively, during that period. The τ decreased 21% in 1993 as compared with 1950. As environmental factors of BC, the intake of animal protein and fat were discussed.